When coupling a coil, which is formed in advance as a closed loop, to an annular stator core, which includes a plurality of radially formed slots having openings open to an inner circumference, so as to form a distributed winding, it is necessary to insert two insertion portions (sides) of each coil into two slots, which are spaced apart in the circumferential direction, while widening the insertion portions in accordance with the groove shape of the slots that widen radially.
In patent document 1, when inserting a coil, which is shaped into a turtle shell form, into slots of a stator core, straight portions of the coil are radially ejected by an ejecting piece to move the straight portions along the slots and insert the straight portion into the slots. Upper and lower end portions of the coil are both formed to be V-shaped. When the straight portions are moved along the slots, the V-shaped portions are deformed to approach the stator core. Patent document 1 describes that the cross-sections of conductor wires forming the coil do not have to be generally circular and may have other shapes, such as a rectangular shape.
Further, patent document 2 discloses a method for manufacturing a stator in which a first side of each of a plurality of coils, which are formed beforehand, is inserted into a slot of a stator core, and a second side of each of the coils is then inserted into another slot so that the coils are spirally overlapped when viewed from an end surface of the stator core. The method of patent document 2 uses a jig having an outer circumference including a plurality of slit-like holding grooves. The plurality of holding grooves include a plurality of first holding grooves, which are arranged at a pitch that is an integral multiple of the pitch of the slots in the stator core, and a plurality of second holding grooves, which are arranged at the same pitch as the first holding grooves. Further, the first side of each coil is inserted into a first holding groove, and the second side is inserted into a second holding groove, which is adjacent to the first holding groove into which the first side is inserted, and the coils are arranged along a circumference of the jig. The jig is arranged at a radially inner side of the stator core, and the first side of each of the coils is ejected outward in the radial direction by an ejecting means and inserted into the corresponding slot of the stator core. Next, the jig is rotated by a predetermined angle relative to the slots of the stator core and positioned so that the second holding grooves are aligned with the corresponding slots of the stator core. Then, the second side is ejected outward in the radial direction by the ejecting means and inserted into the corresponding slot of the stator core.